The present invention relates to the field of devices for nonlinear optics, frequency conversion, optical switching, photoconductivity, photovoltaics, electroluminescence, pressure-sensitive paint and electrochemical sensor using organometallic materials. More particularly, the invention pertains to a series of platinum acetylide nonlinear optical chromophores which are liquid at room temperature.
There has been considerable interest in the synthesis, spectroscopy, nonlinear optics and structure-property relationships of transition metal acetylides. (See e.g., Rogers, J. E.; Cooper, T. M.; Fleitz, P. A.; Glass, D. J.; McLean, D. G. J. Phys. Chem. A 2002, 106, 10108-10115; Cooper, T. M. In Encyclopedia of Nanomaterials and Nanotechnology; Nalwa, H. S., Ed.; American Scientific Publishers, 2004; Vol. 10, 447-470; Liu, Y.; Jiang, S.; Glusac, K. D.; Powell, D. H.; Anderson, D. F.; Schanze, K. S. J. Amer. Chem. Soc. 2002, 124, 12412-12413; Kohler, A.; Wilson, J. S.; Friend, R. H.; Al-Suti, M. K.; Khan, M. S.; Gerhard, A.; Bassler,H. J. Chem. Phys. 2002, 116, 9457-9463; Bruce, M. I.; Davy, J.; Hall, B. C.; Jansen van Galen, Y.; Skelton, B. W.; White, A. H. Appl. Organomet. Chem. 2002, 16, 559-568; Szafert, S.; Gladysz, J. A. Chem. Rev. 2003, 103, 4175-4205; Emmert, L. A.; Choi, W.; Marshall, J. A.; Yang, J.; Meyer, L. A.; Brozik, J. A. J. Phys. Chem. A 2003, 107, 11340-11346; and Yam, V. W.-W. Acc. Chem. Res. 2002, 35, 555-563.) Transition metal acetylides are square planar molecules having the molecular formula cis or trans-M(PR3)2(C≡CR′)2. The R′ group is typically an aromatic substituent. Common R groups include methyl, ethyl, butyl and phenyl, which all give crystallinity. The transition metal M is selected from the group consisting of palladium, platinum, nickel, and mixtures thereof. Platinum acetylides and the polymeric platinum polyynes (Frazier, C. C.; Guha, S.; Chen, W. U.S. Pat. No. 4,879,479,1989; Friend, R.; Kohler, A. U.S. Pat. No. 5,698,048,1997) have been shown to undergo efficient conversion to a broad band absorbing triplet state upon excitation by a laser. In the prior art, polymeric or oligomeric versions of these compounds containing the tributyl phosphine group, P(C4H9)3 (designated as PBu3) have been described. The palladium acetylide polymer (Frazier, 1989, supra)
has been shown to have good optical properties, including high optical nonlinearity and high visible transparency and can be used in devices for nonlinear optics, frequency converters for optical computing and communication. The applicants prepared free standing films by dissolving the polymer and Upjohn polyimide 2080D in 1-methyl-2-pyyrolidone. They spread the solution on a glass plate using a doctor blade and following drying in a vacuum oven for 24 hours obtained a film having 25-120 μm thickness. The film has a measured nonlinear refractive index n2 that is 58 times that of carbon disulfide.
The related transition metal polymer (Friend, 1997, supra)
is used as a photoresponsive material combined with a fullerene. The material is placed in a photoresponsive device consisting of indium/tin oxide coated glass substrate, a polymer/fullerene thin film and an aluminum layer. By mixing the polymer with a fullerene, the efficiency of charge generation following photon absorption increases by lengthening the lifetime of an intermediate neutral excited state. This causes crossing to the triplet state and enhances charge separation. The inventors of this patent show that a mixture of the polymer and C60 quenches the triplet luminescence and enhances carrier photogeneration by a factor of 1000 over devices made with the polymer alone.
The polymers from the prior art are crystalline and have limited solubility. Unfortunately, the low solubility limits the dye concentration to the millimolar range, thereby decreasing device performance. An example of the prior art is the platinum acetylide complex (abbreviated as PE2).

PE2 is a crystalline compound with a melting point of 137° C. (McKay, T. J.; Bolger, J. A.; Staromlynska, J.; Davy, J. R. J. Chem. Phys. 1998, 108, 5537-5541). High concentrations are necessary for the study of phenomena like triplet-triplet annihilation, exciton migration and nonlinear optical properties as well as improved performance when used in optical devices. Solubility problems have prevented the study of high concentration solutions of PE2 and related chromophores.
In order to develop methods for lowering the melting point and increasing the solubility of platinum acetylide chromophores, the applicants used trioctyl phosphine as a reagent for the preparation of the platinum acetylide complexes. Trioctyl phosphine has been used as a reagent and a passivating agent in the synthesis of monodisperse semiconductor nanocrystals (Wuister, S. F.; van Houselt, A.; Donega, C.; Vanmaekelbergh, D.; Meijerink, A. Angew. Chem. Int. Ed. 2004, 43, 3029-3033). Also, trioctyl phosphine-containing catalysts having one Ru atom bonded to two P atoms, in particular bis(acetylacetonato)bis(phosphine)ruthenium complexes have been prepared (Kawakami, K.; Utsunomiya, M.; Takahashi, K. Japan Patent 2003238579 2003). Surprisingly, the applicants have found that platinum acetylide compounds containing this trioctyl phosphine group ligand are liquids at room temperature, thereby making possible the development of devices requiring materials with a high chromophore concentration.